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Address reprint requests and correspondence: Andrew Gallo, Department of Radiology, Brooke Army Medical Center, 3551 Roger Brooke Dr, Fort Sam Houston, San Antonio, TX 78234
Craniofacial trauma accounts for a large number of medical encounters in the United States and is associated with significant morbidity and mortality. The role of imaging, particularly computed tomography (CT) and CT angiography can significantly enhance the evaluation of patients with craniofacial trauma, assisting with appropriate management and surgical planning. Radiologic studies additionally provide information about soft tissue and vascular trauma which cannot always be excluded by physical examination. This article reviews the anatomy of the head and neck, typical fracture patterns, and current imaging techniques in the evaluation of head and neck trauma.
Head and neck trauma is an important topic for both radiologists and surgeons, accounting for a large number of emergency department visits in the United States and associated with substantial morbidity and mortality.
Precise description of facial fractures, associated complications, and violation of facial buttresses assists with appropriate management and surgical reconstruction planning.
Additionally, radiologic studies provide important information about penetrating neck trauma, as some authors believe that physical examination alone is not sufficient to exclude vascular injuries.
Penetrating zone II neck injury: Does dynamic computed tomographic scan contribute to the diagnostic sensitivity of physical examination for surgically significant injury? A prospective blinded study.
This article describes the role of imaging, particularly computed tomography (CT) and CT angiography (CTA) in the evaluation and management of head and neck trauma.
Anatomy
Six-paired bones form the facial skeleton (maxilla, palatine, zygomatic, nasal, lacrimal, and inferior nasal conchae), and 2 unpaired bones (vomer and mandible [technically, the mandible is a paired bone—there is a symphysis]). Characterization of facial fractures by the affected bones can be tedious given their number and complexity. The facial bones have additionally been classified according to a buttress system, highlighting their functional relationships and simplifying them into 4 pairs of vertically and horizontally oriented struts which provide a protective framework for orbital contents, teeth, and nasal cavity. Although precise description of the individual fractured bones is important, conceptualization of facial fracture patterns according to violation of facial buttresses can be useful in planning surgical fixation, as plates/screws are typically anchored in the buttress. Additionally, a description of fractures in proximity to vulnerable soft tissues and functionally relevant structures can help with surgical planning and prediction of complications.
The vertical buttresses include the medial maxillary, lateral maxillary, posterior maxillary, and posterior vertical mandibular buttresses. The medial maxillary facial buttress begins at the nasofrontal suture, extending inferiorly along the lateral margin of the piriform aperture to the maxillary alveolar process and projecting posteriorly to include the medial orbital wall and medial wall of the maxillary sinus. The lateral maxillary buttress begins at the zygomaticofrontal suture, extending inferiorly along the lateral orbital rim, through the body of the zygomatic bone, and across the zygomaticomaxillary suture to end at the maxillary alveolar process. This buttress includes the lateral orbital wall and lateral maxillary sinus wall. The posterior maxillary buttress, important in the description of Le Fort fractures, contains the pterygoid plates, connecting the sphenoid bone to the maxilla. The posterior mandibular buttress includes portions of the mandibular angle, ramus, and condyle.
The horizontal buttresses include the upper transverse maxillary, lower transverse maxillary, upper transverse mandibular, and lower transverse mandibular buttresses. The upper transverse maxillary buttress begins at the nasofrontal suture, extending along the inferior orbital rim (and continuing posteriorly as the orbital floor) across the zygomatic bone to end at the zygomaticotemporal suture. The lower transverse maxillary buttress is oriented horizontally along the maxillary alveolar process, extending posteriorly to include the hard palate. The upper transverse mandibular buttress encompasses the mandibular alveolar process and extends from its posterior margin through the mandibular ramus to the posterior cortical margin of the mandible. The lower transverse mandibular buttress is formed by the inferior margin of the mandible.
Penetrating neck injuries are commonly classified according to zones of injury which are defined by the site of entry, although the trajectory of the penetrating trauma may span multiple zones and/or extend into facial or cranial structures. Zone I, the most inferior, extends from the sternal notch superiorly to the cricoid cartilage and includes segments of the innominate artery and brachiocephalic veins, segments of the subclavian artery and veins, the common carotid and vertebral arteries, esophagus, trachea, and thyroid gland. The aortic arch and lung apices may extend into Zone I. Zone II extends from the cricoid cartilage to the angle of the mandible and contains the common carotid and external carotid arteries, the jugular veins, larynx, esophagus, and pharynx. Zone III extends from the angle of the mandible to the base of the skull and includes the internal carotid and vertebral arteries, branches of the external carotid artery, the internal jugular vein, pharynx, and parotid gland (Buttress Figure 1)
Le Fort fractures are characterized by a variable degree of craniofacial dissociation resulting from a high-force impact on the midface. They were first described by French surgeon Rene Le Fort in the early 20th century.
All Le Fort fracture patterns involve fractures resulting in pterygomaxillary dissociation, usually through the pterygoid plates (although fractures may occur through the posterior maxillary sinuses). Le Fort fractures are differentiated by the anterior facial fractures which define the shape and size of the dissociated facial bony segment. It is important to recognize that multiple Le Fort patterns may occur concurrently and may also differ from side to side (Le Fort Figure 2).
Le Fort type I fractures (“floating palate”), are horizontally oriented and involve separation of the hard palate (lower transverse maxillary buttress) from the remainder of the skull. They extend through the anterior, lateral, and medial maxillary walls into the pterygoid plate. They can be associated with dental fractures and malocclusion due to dissociation of the hard palate from the skull.
Le Fort type II fractures (“pyramidal fracture”) disrupt the medial, lateral, upper transverse, and posterior maxillary buttresses with fracture apex at the nasofrontal suture. They extend through the medial orbital wall, orbital floor, and zygomaticomaxillary suture, sparing the zygomatic bone. Le Fort type III fractures (“craniofacial dissociation”) affect the medial maxillary, lateral maxillary, upper transverse maxillary, and posterior maxillary buttresses, extending from the nasofrontal suture through the medial and lateral orbital walls and zygomatic arch. Le Fort type II and III fractures are distinguished by involvement of the lateral orbital wall and zygomatic arch (type III), as well as involvement of the nasofrontal suture and medial orbital walls (types II and III). Both Le Fort type II and III fractures can be associated with orbital complications and CSF rhinorrhea (Figure 3).
Figure 3Coronal and axial CT images of a trauma patient demonstrating Le Fort II and III fracture patterns and bilateral naso-ethmoidal complex fractures with blood products within the ethmoid sinus.
Naso-orbital-ethmoidal (NOE) fractures typically involve high-energy blunt trauma and are rare as an isolated injury. Up to 60% are associated with zygomaticofacial complex (ZMC) fractures, and up to 20% are associated with pan facial fractures. They all consist of a central fragment (single or comminuted) which extends along 5 fracture lines: the lateral nose and piriform aperture, the nasomaxillary buttress, the inferior orbital rim and floor, the medial orbital wall, and the frontomaxillary suture.
Identification of 4 of the 5 fracture lines must occur to distinguish NOE fractures from other fracture patterns that involve the maxilla and orbits. NOE fractures can be additionally classified by the Markowitz and Manson classification system. Type I involves a single large fracture fragment connected to an intact medial canthal tendon. Type II is comminuted with intact medial canthal tendon attached to a single bone fragment. Type III is comminuted and involves an avulsion of the medial canthal tendon from the anterior medial orbital wall at the level of the lacrimal fossa.
Complications include exophthalmos, telecanthus, and CSF rhinorrhea if the cribriform plate is involved. Diagnosis and grading of NOE fractures rely heavily on CT, as physical examination may underestimate the extent of injury due to facial swelling.
The medial canthal tendon is not directly visualized on CT, so differentiation of Type II from Type III cannot be determined based upon imaging alone. However, the degree of comminution of the medial orbital wall at the level of the lacrimal fossa may raise the suspicion of medial canthal tendon involvement.
ZMC fractures dissociate the zygomatic bone from the midface, involving the lateral maxillary and upper transverse maxillary buttresses, usually resulting from a direct blow. These fractures disrupt the zygomaticofrontal, zygomaticomaxillary, zygomaticotemporal, and zygomaticosphenoid sutures. They are correctly classified as tetrapod fractures, having been historically referred to as tripod fractures prior to the advent of CT, as the lateral orbital wall fragment cannot be discerned on frontal view plain film radiography. Complications include enophthalmos and restricted mouth opening.
ZMC fractures can be classified by the Zingg classification system, a commonly used surgically relevant CT-based grading system. Zingg type A fractures are isolated incomplete fractures of only one limb of the zygoma, involving only the zygomatic arch (type A1), the lateral orbital rim (type A2), or the inferior orbital rim (type A3). Zingg type B are tetrapod fractures with dissociation of the zygoma, and type C fractures are comminuted (Figure 4).
Figure 4Axial and coronal CT images demonstrating comminuted and displaced left zygomaticomaxillary complex fracture with complete opacification of the left maxillary sinus with blood product.
As noted above, craniofacial trauma can involve both typical fracture patterns involving multiple cranial bones or more complex injuries. However, isolated fractures can also occur. Frontal sinus fractures occur more commonly than any other single frontal bone fracture due to decreased thickness of the frontal bone over the sinus. If the fracture extends into the anterior cranial fossa, CSF rhinorrhea, brain herniation, or intracranial infection may occur. Fractures involving the medial aspect of the frontal sinus may extend into the nasolacrimal duct, creating a mucocele. Nasal bone fractures are extremely common due to the superficial location and are classified by anatomic plane. Type I fractures do not involve the nasal septum and are located beneath a plane extending from the caudal tip of the nose to the anterior nasal spine. Type II fractures involve the nasal septum and the anterior nasal spine. Type 3 fractures involve the nasal and orbital bones and sometimes the nasal septum and intracranial structures. Isolated zygomatic arch fractures should be distinguished from ZMC complex fractures, which involve the lateral orbital wall. Isolated zygomatic arch fractures are usually comminuted, and depressed fragments may extend into the infratemporal fossa, causing trismus. Alveolar process fractures are the most common type of maxillary fracture and involve the lower transverse maxillary buttress, commonly due to a direct force to the alveolar process or indirect force through the teeth. Alveolar fractures can cause dental malocclusion, dental intrusion or extrusion, crown or root fracture, or dental root avulsion injuries (Figures 5 and 6).
Figure 5Axial CT image and 3D reconstruction demonstrating displaced fracture of the left mandibular angle.
Figure 6Axial CT image demonstrating penetrating ballistic injury entering the right parasymphyseal maxilla with resulting comminuted maxillary and dentoalveolar fracture. Bullet trajectory extends through the oral cavity through the right parapharyngeal space and right perivertebral space, exiting the right paraspinal region with bullet fragment in the right paraspinal region.
The orbital wall is composed of the medial maxillary, lateral maxillary, and upper transverse buttresses along with the floor of the cranial fossa. Single buttress fractures commonly result in a “blowout” fracture, most commonly involving the inferior wall with the wall displaced away from the orbit. Orbital floor fractures may lead to fat herniation through the defect and entrapment of the inferior rectus muscle.
The “trap door” fracture is a pediatric variant of orbital floor fracture. The higher bone elasticity in younger patients results in recoil of the fracture fragment, entrapping orbital fat and the inferior rectus muscle within the maxillary sinus. The recoil of the fragment commonly results in significant underestimation of the size of the fracture defect.
For this reason, minimally or nondisplaced inferior wall fractures should be recognized and adequately described. The second most common orbital wall fracture involves the medial orbital wall, structurally reinforced by adjacent ethmoid air cells, and can occur in conjunction with an orbital floor fracture. Complications of orbital wall fractures include enophthalmos which results from increased effective orbital volume and more commonly occurs in combined medial/inferior wall fractures as opposed to isolated inferior wall fractures.
However, enophthalmos may not be present acutely if there is significant orbital edema. The reported sensitivity of CT for detection of open globe injury is variable, ranging from 56% to 76%, and specificity ranging from 85% to 100%.
Orbital roof fractures most commonly occur in children secondary to blunt trauma to the forehead or superior orbital rim. In adults, orbital roof fractures usually occur with higher energy facial trauma and may be associated with other ocular or intracranial injuries. Orbital roof fractures may be non-displaced, superiorly displaced (“blow-out or blow-up”), or inferiorly displaced (“blow-in”). Similar to orbital floor fractures, extraocular muscle entrapment may occur, affecting the superior rectus or oblique muscles. A late complication that may occur with children is the growing fracture of the orbital roof. This occurs when CSF pulsations and normal cranial growth cause herniation of meninges and possibly brain parenchyma into the fracture line. This can be recognized on CT as a gradually widening fracture defect over the course of months to years after injury (Figures 7 and 8).
Figure 7CT reconstruction of patient with gunshot wound to face demonstrating comminuted fractures of the left inferior and medial orbital wall extending to the left infraorbital canal, comminuted fracture of the left mandible and maxilla, and fracture involving the left maxillary sinus.
Figure 8Coronal CT image demonstrating displaced fractures of the right inferior and medial orbital walls with herniation of extraconal fat through the osseous defects, a small amount of extraconal air, and displacement of the right inferior rectus muscle to the level of the inferior wall osseous defect.
The mandible is typically fractured in 2 or more locations due to its ring like shape. A single mandibular fracture is likely the result of a fracture-dislocation in which the temporomandibular joint relocates prior to imaging. Upper maxillary buttress fractures, which include the orbital floor, can result in globe injuries and inferior rectus muscle injuries. If the fracture extends through the superior orbital fissure, injury to cranial nerves III, IV, V1, and VI may cause superior orbital fissure syndrome, causing ophthalmoplegia, diplopia, and ptosis. Injury to the optic nerve (CN II) at the orbital apex may cause orbital apex syndrome, a surgical emergency. Injury to cranial nerve V2 is commonly associated with inferior wall blowout fractures and type II Le Fort fractures and results in hypesthesia of the ipsilateral cheek and maxillary gingiva. Lower maxillary buttress fractures and upper mandibular buttress fractures are associated with dental fractures, dental avulsion injuries, tooth devitalization, and malocclusion. Lower mandibular buttress fractures through the mandibular canal can involve the inferior alveolar nerve, resulting in hypesthesia of the ipsilateral lower lip, chin, anterior tongue, and mandibular teeth. Because the medial maxillary buttress is located in close proximity to several important structures (intraorbital contents, frontal recess, sphenoethmoidal recess, osteomeatal complex, lacrimal duct and sac, medial canthal tendon), it is important for the radiologist to detect complications such as sinus drainage obstruction, globe injury, medial canthal tendon injury, epistaxis, CSF rhinorrhea, and lacrimal duct/sac injury. Lateral maxillary buttress fractures can also cause superior orbital fissure or orbital apex syndrome as well as globe injury, extraocular muscle injury, optic nerve injury, or orbital hematoma. Extension of a posterior maxillary buttress fracture posteriorly into the sphenoid bone can result in carotid artery injury or carotid-cavernous fistula.
Penetrating Neck Injuries
After World War II, the management of penetrating neck injuries was informed by the mechanism of injury, location/depth of wound, presence of hemorrhage or airway compromise, and other injuries to the esophagus or pharynx, with many patients undergoing immediate surgical exploration, especially for Zone II injuries, along with other invasive diagnostic tests.
With the advent of multidetector CT, management decisions have been increasingly influenced by CT angiography, which can provide a global assessment of large anatomic regions including the vasculature, bones, airway, and soft tissues as well as information regarding the wound tract.
Some studies suggest that the use of CT imaging in penetrating neck trauma can nearly eliminate negative surgical explorations.
The wound tract may not always be a simple linear tract, due to fragmentation of high-velocity projectiles. Low-velocity injuries commonly have no distinct exit wound. Reformats in nonstandard imaging planes may be useful in accurate visualization of the wound tract and may increase sensitivity for the detection of residual foreign bodies, gas, hemorrhage, edema, or bone fragments.
Arterial injury may occur in 15%-25% of penetrating neck injuries.
Among these arterial injuries, 80% involve the carotid artery and 43% involve the vertebral arteries. Arterial injuries can be particularly devastating and result in stroke. CTA may show partial or complete occlusion, pseudoaneurysm, intimal injuries, arteriovenous fistula, active bleeding, or vessel caliber changes.
Penetrating zone II neck injury: Does dynamic computed tomographic scan contribute to the diagnostic sensitivity of physical examination for surgically significant injury? A prospective blinded study.
However, the total iodinated contrast load will be higher if a patient subsequently undergoes conventional catheter angiography. Although MR angiography can be used in the evaluation of blunt neck injury, its use in penetrating trauma is typically limited by the potential for retained metallic foreign objects, as well as longer imaging times required for MR angiography.
However, limitations include availability, operator dependency, lack of complete visualization of the vertebral arteries and vasculature in Zones I and III, and the lack of overall global anatomic assessment which can be provided by CTA. Venous injuries are commonly missed in the physical examination of penetrating neck trauma.
Penetrating zone II neck injury: Does dynamic computed tomographic scan contribute to the diagnostic sensitivity of physical examination for surgically significant injury? A prospective blinded study.
Similar to arterial injury, CTA can play a significant role in diagnosis.
Because CTA provides anatomic details of the neck soft tissues in addition to vascular anatomy, it can play an important role in demonstrating penetrating or bony injuries of the cervical spine, esophageal injury, and injury to the trachea/larynx. If the esophagus is in close proximity to the wound tract, high suspicion should be raised for injury, even if an esophageal defect cannot be visualized,
prompting further evaluation with esophagography or endoscopy. Although tracheolaryngeal injuries are rare, high suspicion must be maintained due to the possibility of airway compromise, especially if the wound tract is in close proximity.
It should be noted that blunt neck injury can cause similar patterns of injury as penetrating neck trauma to include local soft tissue injury, vascular injury (to include dissection), and fractures. Blunt neck injuries can also be classified by the zones of injury described for penetrating neck trauma. In particular, CT and CTA are most useful in delineating injury patterns and guiding surgical management (Figures 9 and 10).
Figure 9Axial CT images demonstrating blast injury with fragments throughout Zones I, II, and III of the neck and traumatic occlusion of the right internal carotid artery and right jugular vein.
Figure 10Coronal CT image after gunshot wound to the neck demonstrating injury to the right common carotid artery with active extravasation and large neck hematoma.
Craniofacial trauma accounts for a significant number of medical encounters and associated morbidity/mortality in the United States. It is important for the radiologist and surgeon to understand the anatomy, typical patterns of injury, and imaging techniques to appropriately guide clinical and surgical management. In particular, CT and CTA are most useful in delineating injury patterns and guiding management.
Penetrating zone II neck injury: Does dynamic computed tomographic scan contribute to the diagnostic sensitivity of physical examination for surgically significant injury? A prospective blinded study.
Penetrating zone II neck injury: Does dynamic computed tomographic scan contribute to the diagnostic sensitivity of physical examination for surgically significant injury? A prospective blinded study.
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